Ch. 11 Kinetic Molecular Theory
5 assumptions of the kinetic theory of gases.
1. Matter is made of particles. 2. The particles are always moving randomly 3. Collisions between particles are elastic. 4. No forces of attraction or repulsion between particles. 5. KE of the particles is directly proportional to the temperature in Kelvin
Kinetic Molecular Theory
All molecules and atoms are in a constant state of motion
Ammonia (NH3) has a higher surface tension than gasoline. Explain why in terms of intermolecular forces.
Ammonia must have stronger intermolecular forces than gasoline.
KE = ½ mv2 Neon (20.28 g/mol) and Argon (39.94 g/mol) b.If they have the same speed, which has more KE?
Argon
What is the difference in atmospheric pressure in Denver (5, 280 ft. altitude) compared to sea level (zero altitude)?
Atmospheric pressure is lower in Denver.
Are in constant random motion Real gases, Ideal Gases, or Both ideal and real
Both ideal and real
Are made of tiny particles. Real gases, Ideal Gases, or Both ideal and real
Both ideal and real
As the temp. of the substance decreases, the average kinetic energy of its particles
Decreases
Define kinetic energy in the context of KMT
Depends on the speed and mass of particles.
Which is a stronger intermolecular force, dipole-dipole forces or London dispersion forces?
Dipole-dipole forces
Identify the types of IMFs in Polar molecules
Dipole-dipole, London Dispersion Forces
All of the atoms that make up a substance must have the same kinetic energy if the temperature of the substance is held constant. True or False?
False. Temperature measures average kinetic energy, so particles have a range of kinetic energies.
Which phase can be most easily compressed? (solid, liquid or gas)
Gas
Which phase is the least dense?
Gas
Have elastic collisions Real gases, Ideal Gases, or Both ideal and real
Ideal Gases
As the temp. of a substance increases the average kinetic energy of its particles
Increases
Temperature increases as KE ... Temperature decreases as KE...
Increases Decreases
Which phases are considered fluid?
Liquid, gas
Identify the types of IMFs in nonpolar molecules
London Dispersion Forces
Explain why methanol (a polar molecule) has a higher boiling point than ethane (a nonpolar molecule) in terms of intermolecular forces.
Methanol has dipole-dipole forces and London dispersion forces, but ethane has only London dispersion forces. Dipole-dipole forces are stronger than London dispersion forces.
Methanol (boiling point 64.7°C) is a liquid at room temperature and argon (boiling point -185.8°C) is a gas. Which has stronger intermolecular forces?
Methanol.
KE = ½ mv2 Neon (20.28 g/mol) and Argon (39.94 g/mol) a. If they have the same KE, which is moving faster?
Neon
When Particles are heated... (3 things)
Particles move quicker. Take up more space Make more collisions
Define pressure in terms of collisions.
Pressure is caused by the collision of gas particles with a surface.
Have attractive forces between molecules. Real gases, Ideal Gases, or Both ideal and real
Real gases
The average KE of a substance is a measure of ... For that substance
Temperature
One cup of water is 40 °C. A second cup of water is 80 °C. Which will have a faster rate of evaporation?
The 80 °C cup.
Explain why water moves up a straw when you drink a refreshing beverage.
The air pressure in the straw is lower than atmospheric pressure, so atmospheric pressure pushes the water up the straw.
While on a ski trip in Denver (5, 280 ft. altitude), you boil some water to make ramen noodles. How will the boiling point of water in Denver compare to the boiling point at sea level?
The boiling point of water in Denver will be lower.
What happens to the speed of particles of a substance as they are heated?
The speed of particles increases.
Define Elastic collisions
The sum of KE before = sum of KE after the collision.
What is absolute zero? What happens at this Temperature? ________________ for that substance.
The temperature at which particles stop moving. 0 K.
Define Inelastic collisions
some KE is lost to heat and sound.
